Eliminating all shooters ability to shoot over walls, or reducing it to only pre-gunpowder age (when they're actually firing weapons that travel in an arc), would go a very long way toward balancing this game. Mortars and saboteurs would have some use, and the all-too-common advancing wall of shooters that comprises most attacks, until late-Industrial, would be drastically reduced. Unfortunately, it's too late for that, and one to two thirds of people would quit if that were to occur.
Feel free to slag me and make assumptions about my ability(or lack thereof). It's only fair, I do the same with the shooter swarmers too. ; )
Different strokes, rich tapestry, and whatnot.